WASHINGTON, D.C. Trade negotiations with Canada have been “really, really difficult,” achieving no substantial progress so far, says one of the United States’ top negotiators, offering a new glimpse at NAFTA-related tensions between the two countries.

Gregg Doud, the chief U.S. agriculture negotiator, contrasted the Canadian stance with what he suggested was smooth sailing in talks with Mexico, according to agriculture-media coverage of a speech he made this week in Michigan.

The negotiations with Mexico to update the free trade agreement, which resumed Thursday morning in Washington, are “going as well as we can possibly expect right now,” he was quoted as saying by the Hagstrom Report.

“I think we are going to get there with Mexico in a relatively short order.”

The third NAFTA partner is a different matter, Doud told an American Sugar Alliance event in in Traverse City, Mich.

“Canada, O Canada, is what you want to say,” the trade official said, according to a report by Food Business News and Hagstrom. He said long-standing agriculture issues with the Canadians have still not been resolved, an apparent reference to American objections to Canadian supply-management systems for dairy and poultry.

U.S. negotiators “haven’t had market access conversations with Canada of any substance,” the Hagstrom Report quoted Doud as saying. Talks have been “really, really difficult … We have to go to get to a situation where we can bring Canada on board and wrap this thing up.”

Asked about the reports, the office of U.S. Trade Representative Robert Lighthizer raised no objections to their accuracy.

Doud’s comments echo those of Lighthizer himself, who told U.S. senators recently that he was close to a deal with Mexico, but that Canada has not been as willing to compromise.

Canadian embassy spokespeople could not be reached for comment.

Canadian officials have said talk of their alleged inflexibility is simply a negotiating or public-relations tactic by the Americans, and that President Donald Trump’s chief concern about NAFTA is the large American trade deficit with Mexico. They say they have not been part of the U.S.-Mexico talks over the past three weeks because those countries have complex bilateral issues to resolve.

That viewpoint seemed to be confirmed Thursday by Ildefonso Guajardo, Mexico’s economy minister, as he entered the USTR offices for another round of negotiations without Canada. The National Post asked if Canadian officials would be part of the discussions next week.

“Hopefully, but we have to make sure the U.S. and Mexico bilaterals are done,” said Guajardo.

As he left the meeting about two-and-a-half hours later, the minister said the two parties are “as close as possible (to a deal), but we’re still working on it.”

The Mexican delegation has said little about the details of their talks with Lighthizer. But sources say they are near to agreement on the key U.S. demands that more of the content of automobiles imported duty-free under NAFTA be made in North America, and by workers earning at least $16 an hour.

Still unresolved is the U.S. request for a sunset clause that would require the agreement to be re-approved every five years. That’s a red line for both Canada and Mexico – and some U.S. senators and congressmen – who believe it would create uncertainty and deter new investment.

“We are organizing the items by degree of complexity, and sunset will be one of the very last,” Guajardo said Thursday.